1. Field of the Invention
This invention relates to vibration damping metal panels having an excellent post-workability, and more particularly to a vibration damping metal panel which can easily be subjected to post-working such as overhanging, bending, drawing or the like and has excellent vibration damping properties over a temperature range of 0.degree.-140.degree. C. for reducing noises and vibrations generated from vibration members in vehicles such as automobiles, railroads, airplanes and the like, and various machines such as office machines, electric goods, metal working machines and the like.
2. Description of the Prior Art
With the popularization of vehicles such as automobile, railroad, airplane and the like, and machines such as office machine, electric goods and the like, countermeasures against noises and vibrations generated from these vehicles and machines have recently been highlighted as an urgent subject. In particular, it has strongly been demanded to reduce noises and vibrations generated from the vibration members such as members (oil pan, engine cover, ceiling member, floor member, etc.) arranged around motorcar engine, home electric appliances, metal working machines and the like. For this end, many vibration damping metal panels have been proposed or sold in markets up to the present.
When conventional vibration damping metal panels are estimated in response to such a commercial demand, they have the following various drawbacks and as a result, their application range is considerably limited in practice.
It is a most serious drawback that since a material of an intermediate layer used in the commercially available vibration damping metal panel consists mainly of a thermoplastic self-adhesive, cracks are produced in the intermediate layer by impact stress in the post-working or the buckling is apt to be caused at flange portion of the contraction deformation. Further, the adhesion to metal is very poor and consequently the peeling or deviation from the metal plate occurs. Accordingly, it is very difficult to perform a combined press molding of overhanging, bending, drawing and the like. That is, it is difficult to apply the conventional metal panels to members for automobile, office machines, metal working machines and the like being much in demand and requiring a complicated press moldability.
And also, the vibration damping metal panels manufactured by a very simple press molding include such various problems for practical use that the intermediate layer material flows out or produces decomposition and carbonization at a baking step or drying step of paint, creep is produced at a service temperature under static stress, and peeling of the metal plate occurs.
Furthermore, in view of spot weldability, there is a problem that the intermediate layer in the conventional vibration damping metal panel has no electrical conductivity because it consists only of an organic high molecular material and therefore it is difficult to apply such an intermediate layer to member for automobiles having a great expectation of large demands.